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 ajneil March 10, 2013 23:10

meshing in flow separation region

can anyone help me in my turbulent flow problem with sudden expansion pipe. i am using k-e model with standard wall function in fluent. i ve meshed the geometry in gambit and i didnt get t y+ values along the wall above 12.

regards
jose

 Aeronautics El. K. March 11, 2013 17:14

Maybe you could use the Enhanced Wall Treatment.

Quote:
 Originally Posted by ajneil (Post 413003) can anyone help me in my turbulent flow problem with sudden expansion pipe. i am using k-e model with standard wall function in fluent. i ve meshed the geometry in gambit and i didnt get t y+ values along the wall above 12. regards jose

 ajneil March 14, 2013 12:58

1) can u explain how enhanced wall treatment gives better results?
2) is it very herd to mesh in the flow separation region?

 Aeronautics El. K. March 14, 2013 14:19

Using standard wall functions means that you ignore the viscous sublayer and that's why you need a y+ >30 (you may want to take a look here: http://www.cfd-online.com/Wiki/Law_of_the_wall).
If y+ is lower than that, Fluent offers the choice to use the enhanced wall treatment whose details you can read here: http://cdlab2.fluid.tuwien.ac.at/LEH...ug/node514.htm

To mesh the flow separation region you need to have some indication as to where this region is. This can be deduced from experimental data or from a simulation on a coarse grid which you refine at the separation region.

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